Schottky barrier diode has superior characteristics of low turn-on voltage, low power loss, fast recovery time and low junction capacitance compared to a PN junction diode, and thus has been widely used in power and high voltage (HV) technology. Typically, the Schottky barrier diode includes a metal layer and a doped semiconductor layer, and the Schottky barrier is formed at the juncture of the metal layer and the semiconductor layer. Breakdown voltage is improved by placing a guard ring in a semiconductor substrate around the Schottky barrier. Nevertheless, an existing Schottky barrier diode exhibits low forward current. Therefore, how to improve the forward current of the existing Schottky barrier diode becomes an important issue in this field.